Headlight



April 1934- G. A. M. LAMBLlN-PARENT 1,955,597

HEADLIGHT Qriginal Filed Dec. 17, 1929 3 Sheets-Sheet l gin/mantelAprilU, 93 -v s. A. M. LAMBLlN-PARENT HEADLIGHT Original Filed 0 90. 17,1929 3 Sheets-Sheet 2 Q Liv p 1934= G. A. M. LAMBLlN-PARENT 1,955,597

HEADLIGHT 3 Sheets-Sheet 5 ori inal Filed Dec. 17, 1929 I I abl o'znaqaasrakfd/wAe/vazzM/hawr Patented Apr. 17, 1934 HEADLIGHT Gustave AlphonseMarie Lamblin-Parent, Lille, France, assignor, by mesne assignments, toUnited States Holding Corporation, a corporation of Delaware ApplicationDecember 17, 1929, Serial No. 414,749

Renewed September 27, 1933 35 Claims. (or. 240-413) This application isacontinuation in part of my application Serial No. 380,281, filed July23, 1929.

In that application I have disclosed a head- 5 light for motor cars, orthe like, which prevents the formation of stray, or dazzling rays in thebeam of the headlight, and have shown an arrangement in which part ofthe rays of the issuing beam diverge below the horizontal, so as to 1light parts of the road adjacent the vehicle, and

without producing a glaring effect upon the drivers of vehicle coming inthe other direction. Such application also disclosesmeans for givingindications of the position of the vehicle to the 5 drivers of followingvehicles.

My present application is directed more particularly to improvements inthe optical characteristics of the headlight disclosed in my priorapplication, and to improvements in the construc- 39 tion, combinationand arrangement of the parts of such headlight.

One of the objects of my present invention is to improve theconstruction of the lamp and condenser lens mounting.

Another object is to provide an improved construction of the modifiedFresnel lens and the optical system, whereby the concentrated portion ofthe beam is brought into its most useful position therein, and wherebythe divergent part of the beam is improved in intensity and uniformityof spread.

With these and other objects in view, which will become apparent as thedescription proceeds, the invention resides in the construction, com- 35bination and arrangement of parts hereinafter more fully described andclaimed.

In the drawings forming part of this specification,-

Figure 1 represents a vertical central sectional view taken through aheadlight constructed according to my invention.

Figure 2 represents a detail horizontal sectional view on a larger scalethrough the lamp casing.

Figure 3 represents a front face view of the main lens.

Figure 4 represents a rear face view thereof.

Figure 5 represents a fragmentary horizontal sectional view through thelens.

. Figure 6 represents a fragmentary vertical perspective view thereof.

Figure 7 represents a vertical section through the lens, showing theconstruction thereof.

Figure 8 represents a similar view of a modified form.

Figure 9 represents a vertical section of the lens of Figure 7, showingthe light distribution.

Figure 10 represents a similar view through the lens of Figure 8. I

Figure 11 is a view showing the use of the conto denser lens and mirrorin the optical system.

Figure 12 represents a vertical section on a small scale throughthe'beam projected by the lens of Figure 9, taken. at a distance fromthe lens.

Figure 13 represents a similar View of the beam projected by the lens ofFigure 10.

Figure 14 represents a top plan view of the lamp-supporting bracket,removed. Referring more particularly to Figures 1 and 2 of the drawings,the headlight includes a metallic casing A, of general ellipsoidal form,or of other form if desired, havinga forward section 5 and a rearsection 6, which are seperable from each other, the forward sectionbeing shouldered l5 vertically and circumferentially of the headlight asat 7, to receive the forward edge of the rear section which fits oversaid shoulder. The sections are removably retained together by means ofthumb screws 8, the threaded shanks of which pass through openingsprovided in the rear half of the casing into engagement with internallythreaded sleeves 9 screwed into cars 10 which may be cast with the'forward section of the casing, the concave washers 11 being interposedbetween the thumb screws and casing to frictionally retain the former inpositionagainst accidental unscrewing. When the thumb nuts are unscrewedand removed, the rear section of the casing may be slipped ofi of theshoulder '7 to ex-- pose the parts of the headlight contained within-thecasing. Within the casing there is carried an angularly disposed bracketB, which may be a casting, hav ing a tripod support comprising threelugs 12 adapted to fit against the upper of corresponding sets of lugs13 which may be cast upon the upper and the lower inside portion of thefront. casing section, the tripod lugs being retained in place by screwsand washers 14. The bracket B is shown as supported upon the upper setof lugs by its tripod connection, but, if desired, it. may be removedfrom the upper set, turned upsidedown, and supported. upon the lowerset.

The bracket B at its lower end, is provided with a rearwardly extendingcentrally located ring 15, and flanking this and forward of it, a pairof rings 16, such rings being adapted to receive lamp sockets l7,\thelamp 18 mounted in the middle or centrally located socket being used forordinary driving purposes, and the lamps 19 in the flankingsockets beingused, if desired, when dim lights are wanted. Set screws 20 may beutilized to retain the sockets in position. The

side lamps need not be used unless desired, and

indeed, may, if preferred, be left out of the assembly. The connectionsto the lamps may be 7 other desirable manner.

23 may, if desired, not be used in the optical sysmade in any desiredmanner, the terminals 21 on the lamp sockets being provided for thispurpose.

Forward of the lamp 18 is arranged a ring 22, in which is mounted acondensing lens 23, such ring having arms 24 which straddle the bracket13, and which are secured thereon by means of a pin 25 extending throughthe side flanges of the bracket and through openings in the arms 24, andone of such arms has an extension 26 which, by means of a screw 27prevents pivotal movement of the ring on the pin 25 and retains the ringand the condenser lens in a fixed angular position in the optical systemof the headlight.

In the opening at the forward portion of the headlight casing is mounteda lens C, the outer flange of which is held in position between the lip28 at the opening of the casing and the ring 29, at the forward face ofthe lens flange, and a ring 30 at the rear thereof. An arm 31' extendsinto a notch at the top of the le flange for properly positioning thelens in the casing, such am being retained in position beneath theforlug 13.

To the rear of the lamp 18 is. arranged a spherical reflector 32, andthis reflector may be carried by a mounting secured to the central lampsupporting ring 15, or may be supported in The condensing lens tem ofthe headlight, and the same is true of the reflector 32, or either maybe used without the other. If used, however, theyenter into thecombination ofthe optical elements in projecting the desired beam, aswill later appear.-

face 35, and on the upper half of its rear face ,has a series ofsubstantially semi-circular refracting zones 36 and on the lower halfanother series of substantially semi-circular refracting zones 38, therebeing also provided a centrally located bulls eye 40. The retractingzones and the part of the bull's eye in the upper half of the lens, andthe zones and the part of the bulls eye in the lower half of the lens,are separated along the line of the abrupt shoulders 41, which extendsubstantially horizontally and diametrically of the lens across thezones thereof and the bulls eye. The inner corners 3'; of the refractingzones of the lower half of the lens are continuous with those of therespective zones of the upper half of the lens, so that the separatingshoulders merge with the surfaces at the inner corners 3'7. Beginning atthe merging comers, the shoulders increase in width across the rearatingthe upper and lower parts merge with the surface near the center of thebulls eye and. in-

crease in width toward the outer edges, following the increase inthickness of the lower half of the bulls eye toward its outer edges.

The refracting zones and the part of the bulls eye in the upper half ofthe lens have a common principal focal region at X, and are of suchcurvatures as to project into parallel rays, light originating at suchfocal region, the upper portion of the bulls eye and the zones beingstruck from centers 0, along the optical axis OA, forward of the lenswith increasing radii as the outer edge of the lens is approached. Thelower zones, and the lower half of the bulls eye have a common principalfocal region at Y (indicated by the focus of the parallel dotted rays K)a region disposed further from the lens than the focal region X, and areof such curvature as to project, with increasing divergence away fromthe axis, rays originating at the focal region Y, the lower half of thebull's eye, like'the upper half, having its inner face spherical, butbeing struck with a radius substantially three times as long, and thefaces of the lower zones being segments of conic surfaces whose axescoincide with the optical axis of the lens. The dotted line e in Figure7 indicates the base of the generating triangle of one of the lowerzones, the line. (1 the hypotenuse, and the distance i along the opticalaxis indicates the altitude of the generating triangle. The angleopposite the axis in the form shown, for instance, may be approximately5.

With this construction of the lens, and with the light source at theprincipal focal region of the upper zones and upper half of the bullseye, such parts will project light originating at such source intoparallel rays, as indicated at 9 (Figure 9), while the lower zones andlower half of the bull's eye will project rays of increasing divergenceaway from the axis as the outer edge of the lens is approached, asindicated by the rays i, the rays near the central portion of the lowerhalf of the bulls eye being parallel to the axis as at h, and the raysprojected through the outer portion of the last zone of the series onthe lower half being of the greatest spread or divergence, suchgradually increasing spread being accomplished, in connection with thestructure of the lower half of the lens, by the location of the lightsource not at the principal focal region of the lower part of the lens,but

at the principal focal region of the upper part thereof. 7

On the-lower half of the lens, and on opposite sides of the centralportion of the front thereof, are arranged a series .ofverticallydisposed cylindrical flutes 42, to laterally spread the light rayspassing through the end portions or segments of the lower refractingzones on the opposite sides'of the cental lower portion of the lens.Such flutes may be struck with equal radii upon centers equally spacedangularly about a common point on the optical axis as indicated inFigure 5.

The resultant beam projected by this optical system, as indicated inFigure 12, is of high in-- tensity in its upper section, as at Q, beingcomposed therein of parallel rays projected through the upper half ofthe lens, and which reach to distant points on the roadway. In its lowersectiorr, which is abruptly widened horizontally over the upper section,as at r, the beam comprises the lateral portions composed of the widespread rays of less and outwardly'decreasing intensity projected throughthe vertical flutes, and which illuminate the sides of the roads andadjacent gutters or side-walks. The central portion T of the lowersection of the beam, of higher intensity than the portion s, which isprojected through the lower lens section between the fluted portionsthereof, illuminates the roadway with decreasing intensity as the frontof the vehicle is approached. All of the upper half of the lens entersinto the formation of the intense parallel rays for distant illuminationand the lower half .forms the illumination of greater width, withdecreasingintensity towards the vehicle and with increasing spreadtowards the sides of the lower portion of the lens. The spread obtainedby the fluted sections, added to that obtained in the central portion ofthe lower lens section, may give to the lower section of the beam atotal spread of as much as if desired, depending upon the curvaturesused, an adequate spread for emciently lighting the roadway andbordering side-walks and gutters.

The spherical reflector, when utilized with the optical system, asindicated in Figure 11, is preferably arranged with its focus at theprincipal focal. region X of the zones and bulls eye of the upper halfof the lens, to increase the light flux projected through the lens, and,if the condensing lens 23 is used, the latter has its optical axis 0apreferably arranged at an angle with the optical axis of the system,with the top of the condenser inclined forwardly away from the lightsource, to thereby condense the light passing through the Fresnel belowthe upper zones, to increase the in-- tensity of lower portions of thelight beam, as indicated in dotted lines at I, m.

In the form of the system shown in Figure 8, the shape of the bulls eyeis somewhat changed, the lower half having its principal focal region atZ, between the principal focal region X of the upper part of the lensand bulls eye and the principal focal region Y of the lower zones, andthe radius of the upper part of the bulls eye is increased and is struckfrom a point below the optical axis, so that, as shown in Figure 10,with the light source at the principal focal region X, the upper part ofthe bulls eye will project rays n which, as the optical axis isapproached, will converge toward and cross such axis, and the lower partof the bulls eye, will project rays which are parallel adjacent theoptical axis, and which diverge as the points of projection are removedfrom the axis. Thus, the rays which from the upper part of the bulls eyeconverge and cross the axis will fall at angles below the horizontal, tothus lower the position of the socalled hot spot in the projected beam,as indicated at V in Figure 13, and in crossing the f parallel raysprojected by the portion of the lower half of the bulls eye adjacent theaxis, will intensify the upper central part of the lower section of thebeam, as shown. I also so shape the lower zones as to cause the lightrays projected through them to cross each other with equal degrees ofspread for the various zones, with the light projected through one ofsuch zones overlapping that projected through adjacent zones, asindicated by the rays b-c inFigure 10, such zones being struck fromcenters 17 (Figure 8), arranged at decreasing distances below the axisand with decreasing radii, as the outer edge of the lens is approached(except for the outermost zone), and with such exception being ofcylindrical curvature of decreasing radii radially of the lens. Theoutermost zone is preferably struck with a somewhat longer radius thanthe next adjacent zone to bring its projected light well to the edge ofand define the lower section of the beam. The rays from each of thelower zones thus crossing, and overlapping the projec.

tion from adjacent zones, the uniformity of light in the beam projectedby the lower part of the lens is increased, as indicated by the crosshatching on Figure. 13, and at the same time the spread or dispersion ofthe lower part of the beam is retained. In this form of the invention,the upper zones merge with the respective lower zones at their outeredges, the thickness of the upper zones increasing from theirputer edgesinwardly with respect to the respective lower zones, and the abruptshoulders (see M -Figure 8) are reversed in position, being wider at theinner edges of the zones and narrowing toward their outer edges. I

Since this applicationwas filed, I have filed applications Serial Nos.28,876, and 554,111, both of which applications disclose subject-mattercommon to this application and to my application, Serial No. 380,281. Inthis application, however, I am making the broader claims to themodified Fresnel lens disclosed in my said applications, as well asclaims to various structural features thereof, and to the combination ofsuch lens with the condenser, and also the'arrangement in which thelight source is arranged at one of the focal regions of the lens, claimsto other subject-matters being made in my other applications. e

The foregoing detailed description has been given for purposes ofillustration of my invention, and no undue limitation should be deducedtherefrom, it being understood that such variations in the construction,combination and arrangement of parts, are permissible as do not departfrom the spirit of the invention and the scope of the appended claims.

I claim:

1. In a light projector, a modified Fresnel lens having a sphericalfront face, and on its rear face having circular stepped refractingzones, the zones on the upper half of the lens having a principal focalregion, a light source substantially at said focal region, the zones onthe lower half of the lens having a focal region differing from that ofthe zones on the upper half and being of such curvatures as to disperselight fallingon them from the light source, the angles of dis persiongradually increasing from the axis outward, a line of abrupt shouldersextending substantially horizontally and diametrically across the lensbetween the zones, the zones on the lower half being of longer focallength than the zones on the upper half of the lens.

2. In a light projector, a modifibd Fresnel lens having on its rear facean upper set of stepped zones of decreasing curvature outwardly andradially of the lens, such zones having a'principal focal region,andhaving a lower set of stepped zones differing in curvature from theupper zones and having a focal region displaced from that of the upperzones a d being of such curvatures as to disperse light f ling thereonfrom their focal region, the angles of dispersion increasing from theaxis outward, and a line of abrupt shoulders extending substantiallyhorizontally e and diametrically of the lens and separating the upperand lower zones, in combination with a light source arrangedsubstantially at one of said focal regions. 7 l

3. In a light projector, the combination of a modified Frenel lenshaving a convex front face and on its rear face having circular steppedrefracting zones and a centrally located bulls eye,

the zones and bulls: eye on the upper half of the lens having aprincipal focal region, the

zones and bulls eye on the lower half of the lens having a focal region,and being of such curvature as-to disperse light falling on them fromsuch focal region, the angles of dispersion gradually increasing fromthe axis outwardly, a line of abrupt shoulders extending substantiallyhorizontally and diametrically of the lens across the bulls eye andzones, the zones and bulls eye of the lower half being of longer focallength than the zones and bulls eye of the upper half of the lens, incombination with a light source arranged substantially at the principalfocal region of the zones and bulls eye of the upper half.

4. In a light projector, the combination with a modified Fresnel lenshaving a convex front face, and on its rear face having circular steppedrefracting zones and a centrally located bulls eye, the zones in theupper half of the lens and the upper half of the bulls eye having aprincipal focal region, and the zones of the lower half of the lenshaving a focal region displaced from that of the upper lens and being ofsuch curvature as to disperse light falling on them from their focalregion, the angles of dispersion of the lower zones gradually increasingfrom the axis outward, a line of substantially horizontally disposedshoulders extending substantially diametrically of the lens, suchshoulders difi'ering in width between the inner and outer edges of thezones, the zones of the lower half of the lens being of longer focallength than the zones and bulls eye of the upper half, in combinationwith a light source arranged substantially at the principal focal regionof the zones and bulls eye of the upper half of the lens.

5. In a light projector, the combination 05a modified Fresnel lenshaving a convex front face and having on its rear face an upper set ofstepped zones of decreasing curvature outwardly and radially of thelens,and a lower set of stepped zones differing in curvature from thezones of the upper set, a line of abrupt shoulders extendingsubstantially horizontally and diametrically of the lens separating theupper and lower zones,

a central bulls eye of different curvatures in its upper and lowerportions, the upper zones having a principal focal region, and the lowerzones havinga focal region displaced from the focal region of the upperzones, and a light source arranged substantially at the principal focalregion of the upper zones. I o

6. In a motor vehicle headlight, the combination of a modified Fresnellens having a spherical front face and having on its rear face an upperset of stepped zones of decreasing curvature outwardly and radially ofthe lens and a lower set of stepped zones of conic segmental form, aline of abrupt shoulders extending substantially horizontally anddiametrically of the lens separating the upper and lower zones, acentral bulls eye of different curvatures in its upper and lowerportions, sets of vertical cylindrical flutes on the forward face of thelens extending not higher than the line of shoulders and disposed onopposite sides of the lower central portion of the lens, the upper zoneshaving a principal focal region and the lower zones having a focalregion displaced from the focal region of the upper zones,

' and a light source arranged at the principal focal cular stepped zonesof increasing curvature outwardly and radially of the lens, thecurvature of the zones of one section differing from the curvature ofthe zones of the other. section, the focal length of one lens sectionbeing different from the focal length of the other lens section.

8. A modified Fresnel lens having an upper set of refracting zones and alower set of refracting zones, the zones of the lower set varying inourvature among themselves and difiering in refractive powers from thezones of the upper set, and being struck with radii from difierentcenters arranged at decreasing distances below the axis of the lens andwith decreasing length of radius as the outer edge of said lens isapproached.

9. A modified Fresnel lens having upper and lower sections, each formedwith refracting zones of varying curvatures, the upper section having afocal region different from that of the lower section, the curvature ofthe zones of one section differing from the curvature of the zones ofthe other section and a centrallyv located bulls eye, part of said bullseye having a focal region between the focal regions of the upper andlower sections of the said lens.

10. A modified Fresnel lens having upper and lower sections, each formedwith refracting zones varying in curvature, a centrally located bullseye divided into upper and lower parts, the up per section and the upperpart of the bulls eye having a focal length different from that of thelower section and the lower part of the bulls eye, the curvature of thezones of one section diiiering from the curvature of the zones of theother section.

11. A, modified Fresnel lens having an upper section and a lowersection, the upper section being formed with refracting zones difieringin ourvature with respect to each other, the lower section of the lensbeing formed with refracting zones differing in curvature with respectto each other and to the zones of the upper section, a centrally locatedbulls eye divided into upper and lower parts, the radius of the upperpart of said bulls eye being struck from a point below the optical axisof the lens.

12. A modified Fresnel lens having an upper set of retracting zones anda lower set of re- Iracting zones, the zones of the lower set varying incurvature among themselves and differing in refractive powers from. thezones of the upper set, each zone being struck with a radius from adifierent center, and a centrally located bulls eye, part of said bullseye being struck with a longer radius than the zones of the lens.

13. Ina light projector, a modified Fresnel lens having upper and lowersections each formed with retracting zones varying in curvature withrespect to each other, and with respect to the zones of the othersection, a light source, the upper section projecting rays from saidlight source into a substantially horizontal beam, and the lower sectionprojecting rays from said light source downwardly and laterally, thezones of the lower section being struck from centers arranged atdecreasing distances below the axis of the lens, and with decreasingradii whereby the light rays from the various lower zones will crosseach other with substantially equal degrees of spread, and the raysprojected through one zone will cross those projected through adjacentzones.

14. A modified Fresnel lens having upper and lower sections, each formedwith refracting zones, the zones of the upper section being of varyingcurvature and differing from the zones 15 of the lower section, the rearfaces of the zones of the lower section being substantially segments ofconicsurfaces having axes of rotation substantially coinciding with theoptional axis of the lens.

15. A modified Fresnel lens having an upper section and a lower section,thelower section being formed with refracting zones differing incurvature with respect to each other, the upper section of the lensbeing formed with refracting zones diifering in curvature with respectto each other and to the zones of the lower section, the zones of theupper section merging with the respective zones of the lower section attheir outer edges and being increased in thickness inwardly with respectto the respective zones of thelower section and forming shouldersbetween the zones of the upper and lower sections.

16. A modified Fresnel lens having upper and lower sections, each formedwith refracting zones, the zones of the one section being of varyingcurvature and differing from the zones of the other section, the innercorners of the refracting zones of the upper section merging with thoseof the respective zones of the lower section, and a line of abruptshoulders separating the upper and lower sections, said shouldersbeginning at the merging corners of said refracting zones and increasingin width'toward the outer edges of the zones;

17. In a light projector, in combination, a modified Fresnel lensdivided into an upper section and a lower section of stepped refractingzones of varying curvature and of different power, and a centrallydisposed two-halves bulls eye, the zones and the half bulls eye in theupper section of the lens having a focal region, the zones and the otherhalf bulls eye in the lower section of the lens having a different focalregion, and a light source arranged substantially at one of said focalregions.

18. In a light projector, a. unitary modified Fresnel lens having upperand lower sections, each formed with refracting zones of varyingcurvatures, the upper section having a focal length different from thatof the lower section, the curvature of the zones of one sectiondiffering from the curvature of the zones of the other section, and aline of abrupt shoulders extending substantially horizontally anddiametrically of the lens separating the upper and lower sections.

19. In a light projector, in combination, a

' modified Fresnel lens having upper and lower sections, each formedwith refracting zones varying in curvature, the uppersection having afocal region difierent from that of the lower section, the curvature ofthe zones of one section difiering from the curvature of the zones ofthe source.

other section, the lens being formed with fiutings, said fiutings beingstruck with equal radii on centers equally spaced angularly about acornmon point on the optical axis of said lens.

v 20. In a light projector, the combination of a modified Fresnel lenshaving upper and lower sections, each formed with refracting zones ofvarying curvatures, the upper section having a focal length difierentfrom that of the lower sec- I tion, the curvature of the zones of onesection difi'ering from the curvature of the zones of the other section,a light source in the region of the foci of the sections, a second lightsource at one side of the first said light source, and a third lightsource at the other'side of said first light 21. In a light projector,the combination of .a modified Fresnel lens having an upper and a lowerset of refracting zones, with the refracting zones of the upper setvarying in curvature with respect to each other and with respect to therefracting zones of the lower set, a light source, and a condensing lensinterposed between said Fresnel lens and said light source.

22. A light projector including in combination, a modified Fresnel lenshaving a spherical front face and having on its rear face an upper setof stepped zones of difierent curvatures outwardly and radially of thelens, and a lower set of stepped zones of difiere'nt refractive power, abulls eye disposed centrally of the lens, a series of verticalcylindrical fiutes on the front face of the lens extending below thehorizontal axis of the lens, the lower refracting zones having a commonfocal region diiferent from the focal region of the upper refractingzones beyond the focal region of the upper zones in a direction awayfrom the lens, and a condenser between said source of light and saidlens.

23. In a light projector, the combination of a modified Fresnel lenshaving upper and lower sections; each formed with refracting'zones ofvarying curvatures, the upper section having a focal length difierentfrom that of the lower section, the curvature of the zones of onesection differing from the curvature of the zones of the other section,a light source, a condensing lens interposed between said Fresnel lensand said light source, and a reflector behind said light source.

24. A concavo-convex lens comprising two half Fresnel lenses in oneunit, the lens halves being provided with refracting zones, the zones ofthe one half varying in curvature from the zones of the other half, thezones of each half varying in curvature among themselves, the focallength of one lens half being different from the focal length of theother lens half.

25. In a light projector, a modified Fresnel lens having upper and lowersections each formed with refracting zones of varying curvature, theupper section having "a focal length diifering from that of the lowersection, the curvature of the zones of one section diifering from thecurvature of the zones of the other section, a light source positionedin the region of the foci, and a reflector behind the light source andadapted to collect light from the source and direct it onto the lens.

26. A unitary modified Fresnel lens having upper and lower sections,each formed with refracting zones-of varying curvature, the upper sec-27. A modified Fresnel lens divided on the 'horizontal median line intoan upper half and a lower half, the upper half being formed withrefracting steps differing in curvature with respect to each other, thelower half of the lens being formed with refracting steps differing incurvature with respect to each other and to the steps of the upperhalf,each step of the lens being of substantially uniform refractive power.

28. A light projector comprising a modified Fresnel lens having aplurality of sections, one .of which above the horizontal axial planehas a difierent focal region from another section below said plane, boththe sections of the lens having refracting zones, the curvature of thezones of each of said sections varying relatively to each other and tothe zones of the other section, and a light source in the region of thefool, the formation of the refracting zones of the sections of the lensmaking the projected beam from the lens as a whole relativelyinsensitive to limited varying relations between the light source andthe foci of the lens sections.

29. In a light projector, a unitary modified Fresnel lens having upperand lower sections, each formed with refracting zones of dififerentcurvatures, the upper section having a focal length difierent from thatof the lower section, the curvature of the zones of one sectiondifiering from the curvature of the zones of the other section, and alight source positioned in the region of the foci. V

30. A modified Fresnel lens having an upper section and a lower section,the lower section being formed with retracting zones differing incurvature with respect to each other, the upper section of the lensbeing formed with refracting zones differing in curvature with respectto each other and to the zones'of the lower section, each zone being ofsubstantially uniform refractive power.

31. A modified Fresnel lens having an upper set of retracting zones anda lower set of curved retracting zones, the zones oi the lower setvarying in curvature among themselves and differing in refractive powersfrom the zones of the upper set, each complete zone being struck with aradius from a different center.

32. A modified Fresnel lens having an upper and a lower set ofretracting zones, the zones of the upper set varying in curvature amongthemselves and being struck with radii from various centers anddifiering in refractive powers from the zones of the lower set, some ofsaid centers I lying substantially on the axis of the lens and somebelow the axis thereof.

33. A unitary modified Fresnel lens having upper and lower sections,each section formed with refracting zones of varying curvature, theupper section having -a focal length different from that of the lowersection, the curvature of the zones of the one section difiering fromthe curvature of the zones of the other section, the lens being formedwith fiutings for lateral light diffusion.

3%. A modified Fresnel lens having an upper and a lower set ofretracting zones, the zones of the upper set varying in curvature amongthemselves and difiering in curvature from the zones of the lower setand being strucl; with radii from various centers, the zones of thelower set being also strucl; with radii from various centers, some ofthe latter centers lying substantially below the axis of the lens.

35. in a light projector, a Fresnel-lens having its rear face dividedinto an upper set a lower set, of stepped rei'racting zones, the zoneslOii from the zones of the lower set, the zones of each set difieringamong themselves in curva-' ture radially of the lens.

GUSTAW AL'PHONSE RQAPUE LAMBllN-PAREEW.

